Spin tunnel magneto-resistance effect type magnetic sensor and production method thereof

ABSTRACT

A magnetic sensor utilizing a spin tunnel magneto-resistance effect (TMR), comprising a tunnel insulating film, a first magnetic layer formed on one of the planes of the tunnel insulating film, a second magnetic layer formed on the other plane of the tunnel insulating film, a third magnetic layer containing an anti-ferromagnetic substance for fixing magnetization of the second magnetic layer, a second insulating film formed on at least one of the first and third magnetic layers and having an opening in a predetermined region, a first electrode electrically connected to one of the first and third magnetic layers only in the opening of the second insulating film, and a second electrode for causing a current to flow between the first electrode and itself through at least the first and second magnetic layers and the first insulating layer.

[0001] This is a continuation of application Ser. No. 09/650,734 filedAug. 30, 2000, which is a continuation of application Ser. No.09/302,228 filed Apr. 29, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to a magnetic sensor, and moreparticularly to a magnetic head and a magnetic memory used for computersand information processing units.

[0004] 2. Description of the Related Art

[0005] Magnetic recording media have been predominantly magnetic disksand magnetic tapes. They are manufactured by forming a thin magneticfilm on an Al substrate or a resin tape. A magnetic head utilizing anelectromagnetic conversion operation is used in order to write and readmagnetic information to and from these magnetic media. This magnetichead comprises a write portion for writing the magnetic information tothe recording medium and a read portion for reading out the magneticinformation from the recording medium. A so-called “induction typehead”, which comprises a coil and magnetic poles that wrap the coil fromabove and below and are electrically connected to the coil, is generallyused for the write portion. Magneto-resistance effect (MR) heads havebeen proposed recently for the read portion so as to cope with themagnetic information having a high recording density. Among the MRheads, those heads which utilize the gigantic magneto-resistance effect(GMR) are well known nowadays.

[0006] Recently, a magnetic sensor using a ferromagnetic tunnelmagneto-resistance effect (spin tunnel magneto-resistance effect: TMR)has been proposed for a magnetic memory as described in JP-A-10-4227.This TMR can obtain a greater resistance change ratio by causing acurrent to flow in a direction of film thickness of themagneto-resistance effect film than the conventional magneto-resistanceeffect devices such as the GMRs which cause a current to flow in adirection of the main plane of the magneto-resistance effect film.

[0007] According to the construction described in JP-A-10-4227, however,an upper electrode stack 30 comprising at least a free ferromagneticlayer 32 and a protective layer 34 must be formed inside a contact holedefined in an insulating layer 40. Therefore, production is difficult,and film quality and film thickness of each layer inside the contacthole are likely to fluctuate from a desired level.

SUMMARY OF THE INVENTION

[0008] In view of the problems described above, the present inventionaims at providing a construction of a magnetic sensor using a spintunnel magneto-resistance effect (TMR) which construction can bemanufactured more easily than the prior art devices and can stably keepfilm quality and thickness at a desired level, and a method of producingthe magnetic sensor.

[0009] To accomplish the object, a spin tunnel magneto-resistance effectmagnetic sensor according to the present invention comprises a firstinsulating film which allows a current to tunnel and flow therethrough,a first magnetic layer formed on a first surface of the first insulatingfilm and containing a ferromagnetic substance, a second magnetic layerformed on a second surface of the first insulating film and containing aferromagnetic substance, a third magnetic layer formed on the secondmagnetic layer and containing an anti-ferromagnetic substance for fixingmagnetization of the second magnetic layer, a second insulating filmformed on at least one of the first and third magnetic layers and havingan opening in a predetermined region, a first electrode electricallyconnected to one of the first and third magnetic layers only inside theopening of the second insulating film, and a second electrode forcausing a current to flow between at least one of the first and secondmagnetic layer and the first electrode through the first insulatingfilm.

[0010] A method of producing a spin tunnel magneto-resistance effecttype magnetic sensor having a first magnetic layer containing aferromagnetic substance, a second magnetic layer containing aferromagnetic substance and a third magnetic layer containing ananti-ferromagnetic substance for fixing magnetization of the secondmagnetic layer according to the present invention comprises the steps of(a) forming the third magnetic layer over a substrate by sputtering, (b)forming the second magnetic layer on the third magnetic layer bysputtering, (c) processing at least the second and third magnetic layersinto a first pattern, (d) forming a first insulating film, which allowsan electric current to tunnel and flow therethrough, on at least thefirst pattern, by sputtering, (e) forming a first magnetic layer on thefirst insulating film by sputtering, (f) processing at least the firstmagnetic layer and the first insulating film into a second pattern, (g)forming a second insulating film in at least a predetermined region ofthe second pattern, (h) forming an opening in a predetermined region ofthe second insulating film and (i) forming a first electrode, which iselectrically connected to the first magnetic layer only inside theopening of the second insulating film, and forming a second electrodeelectrically connected to the second magnetic layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a perspective view showing a magnetic head according toa first embodiment of the present invention;

[0012]FIG. 2 is a sectional view showing a part of the magnetic headaccording to the first embodiment of the present invention;

[0013]FIG. 3 is a sectional view showing a part of a magnetic headaccording to a second embodiment of the present invention;

[0014]FIG. 4 is a sectional view showing a part of a magnetic headaccording to a third embodiment of the present invention;

[0015]FIG. 5 is a sectional view showing a part of a magnetic headaccording to a fourth embodiment of the present invention;

[0016]FIG. 6 is a sectional view showing a part of a magnetic headaccording to a fifth embodiment of the present invention;

[0017]FIG. 7 is a sectional view showing a part of a magnetic headaccording to a sixth embodiment of the present invention;

[0018]FIG. 8 is a sectional view showing a part of a magnetic headaccording to a seventh embodiment of the present invention;

[0019]FIG. 9 is a sectional view showing a part of a magnetic headaccording to an eighth embodiment of the present invention;

[0020]FIG. 10 is a perspective view showing a magneticrecording/reproducing apparatus using the magnetic head according to theembodiments of the present invention;

[0021]FIGS. 11A to 11G are sectional views each showing a productionstep of the magnetic head shown in FIG. 4;

[0022]FIGS. 12A to 12G are sectional views each showing a productionstep of the magnetic head shown in FIG. 8;

[0023]FIG. 13 is a sectional view showing a magnetic memory according toone embodiment of the present invention; and

[0024]FIG. 14 is a plan view showing the magnetic memory according toone embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] Several embodiments of the present invention, wherein a magneticsensor according to the present invention is applied to a reproducingmagnetic head, will be explained initially.

[0026] The recording/reproducing head used in the first embodimentincludes a reproducing TMR head utilizing a TMR (spin tunnelmagneto-resistance effect) and an induction type recording thin filmmagnetic head. The reproducing TMR head is mounted onto a substrate, andthe recording thin film magnetic head is mounted onto the TMR head.

[0027] This embodiment employs the construction for preventing a currentflowing through a magneto-resistance effect film of the reproducing TMRhead from leaking to a magnetic domain control layer, and improvesdetection efficiency of a resistance change ratio of themagneto-resistance effect film. Also, this embodiment reduces the widthof the region, in which the current of the magneto-resistance effectfilm flows, by reducing the width of electrodes which are in contactwith the magneto-resistance effect film, and reduces a track width, too.In this way, this embodiment provides a reproducing TMR head capable ofcoping with a magnetic recording medium having a higher recordingdensity.

[0028] The construction of the reproducing TMR head according to thefirst embodiment will be explained more concretely with reference toFIGS. 1 and 2. The recording thin film magnetic head is disposed insuperposition with the reproducing TMR head. The explanation of theconstruction of this thin film magnetic head will be omitted herebybecause it is well known in the art.

[0029] A lower shield film 10 is formed on a ceramic substrate 31 asshown in FIG. 1. An electrode film 8 patterned into a desired shape isdisposed on the lower shield film 10. A magneto-resistance effect film20 having a four-layered structure is disposed on and at a part of theelectrode film 8. Magnetic domain control films 7 are arranged on bothsides of the magneto-resistance effect film 20 and an insulating film 6is disposed on the magneto-resistance effect film 20 and the magneticdomain control films 7 in such a fashion as to bury them. As shown inFIG. 2 which is a sectional view taken along a line A-A′ of FIG. 1, athrough-hole (opening) 21 is bored in the insulating film 6 at aposition which is situated on the magneto-resistance effect film 20. Anelectrode film 5 is arranged on the insulating film 6 and keeps contactwith the magneto-resistance effect film 20 at only the through-holeportion 21. Therefore, when a current is caused to flow from theelectrode film 5 to the electrode film 8, this current flows from theportion, at which the electrode film 5 is in contact with themagneto-resistance effect film 20, to the magneto-resistance effect film20 in the direction of film thickness. Consequently, the width of theregion of the magneto-resistance effect film 20, in which the currentflows, is limited substantially to the width of the through-hole 21 andthis width practically serves as a track width. Incidentally, an uppershield film 9 (not shown in FIG. 1) is disposed on the electrode film 5.The shield films 9 and 10 are disposed in order to magnetically shield aleakage flux from the recording medium and to improve spatial resolutionof the reproducing head.

[0030] The magneto-resistance effect film 20 has the four-layeredstructure comprising a ferromagnetic free layer 3, an electricalinsulating layer 1, a ferromagnetic fixing layer 2 and ananti-ferromagnetic layer 4 that are laminated in order named. The freelayer 3 and the fixing layer 2 are formed in such a fashion that theiraxes of easy magnetization are parallel. Magnetization of the fixinglayer 2 is fixed to a predetermined direction due to its magneticexchange/coupling with the anti-ferromagnetic film 4. When thereproducing TMR head opposes the magnetic recording medium,magnetization of the free layer 3 rotates in accordance with thedirection of magnetization of the magnetic information recorded on themagnetic recording medium. Therefore, the direction of magnetization ofthe free layer 3 is parallel, or anti-parallel, to the direction ofmagnetization of the fixing layer 2. When the current is caused to flowthrough the magneto-resistance effect film 20 in the direction of filmthickness through the electrode films 5 and 8, the current flows whiletunneling through the insulating film 1. The electric resistance of themagneto-resistance effect film 20 changes depending on whether thedirections of magnetization of the free layer 3 and the fixing layer 2are parallel or anti-parallel to each other, due to the spin tunnelmagneto-resistance effect (TMR). In other words, the tunnel currentchanges depending on the relative direction of the spin of magnetizationin the free layer 3 and in the fixing layer 2. The recorded signal canbe reproduced by detecting this change.

[0031] The magnetic domain control film 7 is a ferromagnetic film forapplying a bias magnetic field to the free layer 3 in order to restrictthe occurrence of the magnetic domain of the free layer 3. Thisembodiment employs the positional relationship such that the uppersurface of each magnetic domain control film 7 is always positionedbelow the upper surface of the insulating layer 1 (on the side of thesubstrate 31 shown in FIG. 1) and that the fixing layer 2 and eachmagnetic domain control film 7 are out of mutual contact. Because themagnetic domain control film 7 has a low resistivity, a part of thecurrent flowing from the electrode film 5 to the electrode film 8 willleak from the fixing layer 2 to the electrode film 8 through themagnetic domain control film 7 without tunneling through the insulatingfilm 1 if the magnetic domain control film 7 keeps contact with thefixing layer 2. The construction shown in FIG. 2 can prevent the leak ofthe current because the fixing layer 2 and the magnetic domain controlfilms 7 are out of mutual contact.

[0032] Next, the material of each part will be explained. The lowershield film 10 is made of Co type amorphous alloys such as CoNbZr, NiFealloys, FeAlSi alloys or CoNiFe alloys. The film thickness is from 1 to5 μm. The upper shield film 9 is made of NiFe alloys or CoNiFe alloysand the absolute value of its magneto-restriction constant is notgreater than 5×10⁻⁶. The upper shield film 9 can be used also as thelower core of the recording thin film magnetic head and in this case,the upper shield film 9 may be a multi-layered film comprising aferromagnetic layer and an oxide, or a ferromagnetic alloy film thatcontains a metalloid such as B or P. In addition, the upper shield film9 preferably has a high resistivity (at least 40 μΩ·cm) so as to improvehigh frequency characteristics of the recording thin film magnetic head.

[0033] Since the electrode film 8 serves as the base film of themagneto-resistance effect film 20, it must be an electrode film whichstabilizes the characteristics of the magneto-resistance effect film 20and provides a high resistance change amount. More concretely, thesurface of the electrode film 8 is preferably flat and clean and when ahigh current density is taken into consideration, the electrode film 8is preferably made of a material having a high melting point. Therefore,the electrode film 8 is formed by sputtering or vacuum deposition ofthose elements, as low resistivity materials, which have a high meltingpoint but exhibit low exothermy, such as Ta, Nb, Ru, Mo, Pt, Ir, etc,alloys containing these elements, such as Ta alloys, TaW alloys, oralloys of W, Cu, Al, and so forth. The thickness of the electrode film 8is from 3 to 30 nm and is changed in accordance with the spacing betweenthe shield film 10 and the shield film 9. The smaller the thickness ofthe electrode film 8, the smaller becomes the spacing between the shieldfilm 10 and the shield film 9, and the higher becomes resolution of thereproducing TMR head. This electrode film 8 may be a multi-layered film(e.g. a multi-layered structure of Ta layer/Pt layer/Ta layer or Talayer/Cu layer/Ta layer).

[0034] The electrode film 5 may be made of the same material as that ofthe electrode film 8.

[0035] The free layer 3 of the magneto-resistance effect film 20 mayhave a single layered structure made of a ferromagnetic material such asa NiFe alloy, a Co alloy, a FeCo alloy or a CoNiFe alloy, or amulti-layered structure containing a ferromagnetic layer for preventingdiffusion on the interface or restricting anisotropic dispersion.Examples of the multi-layered structure include a structure of Colayer/NiFe layer/Co layer and a multi-layered structure of a Colayer/NiFe alloy layer/CoFe layer. Which material is used for the freelayer 3 and whether the free layer 3 uses the single layer structure orthe multi-layered structure are determined also by the combination withthe electrode film 8 as the base. The fixing layer 2 can be made of Coor a Co alloy, or may be made of the same material or may have the samestructure, as that of the free layer 3. The fixing layer 2 may alsocomprise a multi-layered structure of a magnetic layer(s) and anonmagnetic layer(s). For example, it may comprise a multi-layeredstructure of ferromagnetic layer/nonmagnetic layer/Co layer such as Colayer/Ru layer/Co layer. The anti-ferromagnetic layer 4 may be made ofIrMn, CrMn type alloys (such as CrMnPt, CrMnRu and CrMnRh), MnRh alloys,MnPt alloys, MnPtPd alloys, NiMn alloys, NiMnPd alloys, MnRhRu alloys,NiO, CoO alloys, Fe₂O₃ and Fe₃O₄ alloys and a CrAl alloy. Alternatively,the anti-ferromagnetic film 4 may comprise a multi-layered film made ofthe combination of these materials. The film thickness is 3 to 10 nm forthe free layer 3, 1 to 10 nm for the fixing layer 2 and 2 to 25 nm forthe anti-ferromagnetic film 4. These films can be formed by sputtering.

[0036] The insulating layer 1 of the magneto-resistance effect film 20is made of any of an oxide, a nitride, a fluoride and a boride, or amaterial containing any of them. For example, it is made of Al₂O₃, SiO₂,Ta₂O₅, TiO₂ or an oxide having a perovskite structure, or a mixed phaseof any of these oxides, to which nitrogen is partly added, and anitride. The insulating layer 1 may be a multi-layered film. Thethickness of the insulating layer 1 is extremely small, for example, 0.2to 3 nm.

[0037] On the other hand, the insulating film 6 is made of Al₂O₃ orSiO₂. An insulating film having a high dielectric withstand voltage canbe obtained by employing a multi-layered structure of a non-magneticmetal film/oxide film/non-magnetic metal film or a ferromagnetic metalfilm/oxide film/ferromagnetic metal film. For example, the insulatingfilm 6 may have a multi-layered structure of an Al film/Al₂O₃ film/Alfilm and a multi-layered structure of a Ni film/NiO film/Ni film or a Cofilm/CoO film/Co film. The insulating film 6 can be made of an oxidecontaining at least one of Ti, Sr and Ba. Among them, the filmcontaining Ti, Sr or Ba becomes a film containing the perovskitestructure and can improve the dielectric withstand voltage.

[0038] The magnetic domain control film 7 comprises a Co type hardferromagnetic film. A film of Cr, Nb or Ta as a non-magnetic metal maybe disposed as the base of the magnetic domain control film 7.

[0039] Incidentally, the width of the through-hole 21 of the insulatingfilm 21 is preferably as small as possible because it determines thetrack width. The production process for this purpose may be as follows,for example. The lower shield film 10 and the magneto-resistance effectfilm 20 are formed first on the substrate 31. After themagneto-resistance effect film 20 is etched by milling method, themagnetic domain control films 7 are then formed. The magnetic domaincontrol films 7 formed on the magneto-resistance effect film 20 areremoved by lift-off. The insulating film 6 is formed. It is formed bysputtering or CVD. Next, this insulating film 6 is etched by RIE(Reactive Ion Etching) and the through-hole 21 is formed. The etchingcondition at this time is of importance. Namely, a CHF₃ or chlorine gasis used for etching so that the width of the through-hole 21 becomessmall. After the electrode film 5 is formed, the through-hole 21 isfilled with this electrode film 5. The surface of the electrode film 5is processed into a flat surface by etching or CMP (Chemical MechanicalPolishing) and the upper shield film 9 is formed by sputtering orplating on this flat electrode film 5. Thereafter, the recording thinfilm magnetic head is formed on the upper shield film 9.

[0040] Next, the explanation will be given on the reproducing operationof the magnetic information of the recording medium by using thereproducing TMR head having the construction shown in FIGS. 1 and 2.First, the float-up surface 32 of the magneto-resistance effect head iscaused to float above the recording medium so that the float-up surface32 and the recording medium oppose each other with a small spacingbetween them. The direction of magnetization of the fixing layer 2 doesnot change because it is fixed by magnetic exchange/coupling with theanti-ferromagnetic film 4. On the other hand, magnetization of the freelayer 3 rotates with the direction of magnetization of the magneticinformation of the recording medium. In consequence, the direction ofmagnetization of the fixing layer 2 and the direction of magnetizationof the free layer 2 are either parallel or anti-parallel to each otherdepending on the magnetic information of the recording medium. When thecurrent is caused to flow between the electrode films 5 and 8, thecurrent flows in the direction of film thickness while tunneling throughthe insulating layer 1 of the magneto-resistance effect film 20. Theelectric resistance of the magneto-resistance effect film 20 at thistime varies depending on whether the direction of magnetization of thefixing layer 2 and that of the free layer 3 are parallel oranti-parallel, due to the spin tunnel magneto-resistance effect. Thismeans that the magnetic information of the recording medium can bereproduced by detecting the current between the electrode films 5 and 8and by detecting the resistance change ratio. Incidentally, when themagnetic information is recorded to the recording medium, theinformation is recorded by the recording thin film magnetic head mountedonto the reproducing TMR head by floating the float-up surface 32 overthe recording medium.

[0041] In the reproducing TMR head of the first embodiment describedabove, the width of the electrode film 5, which is in contact with themagneto-resistance effect film 20, is decreased by the insulating film 6and the track width is set to a width smaller than that of themagneto-resistance effect film 20. Therefore, the track width can benarrowed easily without reducing the width of the magneto-resistanceeffect film 20 and the recording density of the magnetic disk of themagnetic recording/reproducing apparatus can be increased.

[0042] Since the magnetic domain control film 7 and the fixing layer 2have the positional relationship such that they are out of mutualcontact, it becomes possible to prevent the current from leaking fromthe fixing layer 2 to the electrode film 8 through the magnetic domaincontrol film 7. Since the current flowing through the magneto-resistanceeffect film 20 in the direction of film thickness can be increased inthis way, the quantity of the current that contributes to the detectionof the resistance change ratio of the magneto-resistance effect film 20due to the spin tunnel magneto-resistance effect increases, anddetection efficiency of the resistance change ratio can be improved.

[0043] As described above, the first embodiment can provide areproducing TMR head which can cope with a high recording density andmoreover, has high detection efficiency of the resistance change ratio.

[0044] Next, a reproducing TMR head according to the second embodimentwill be explained with reference to FIG. 3.

[0045] In FIG. 3, like reference numerals are used to identify likelayers and like films having the same functions as in FIG. 2. A largedifference of the reproducing TMR head shown in FIG. 3 from thereproducing head of FIG. 2 resides in that both end portions of themagneto-resistance effect film 20 are so arranged as to hang on themagnetic domain control films 7. According to this construction, theinsulating layer 1 always exists between the free layer 2 and themagnetic domain control films 7, so that the leakage current from thefree layer 2 to the magnetic domain control films 7 can be preventedmore effectively. Therefore, the magnetic domain control films 7 can becomposed of a film having a low resistivity (CoCr alloy film). In theconstruction shown in FIG. 3, the upper shield film 9 is used also asthe upper electrode film 5, and the production process can be simplifiedeventually.

[0046] When the insulating film 6 is made of SiO₂ and the through-hole21 is formed by RIE using CHF₃ as the etching gas in the constructionshown in FIG. 3, the width (track width) of the through-hole 21 that canbe formed is from 0.2 to 0.3 μm. This track width can achieve a highrecording density of 20 Gb/in² or more.

[0047] Next, a reproducing TMR head according to the third embodimentwill be explained with reference to FIG. 4.

[0048] In FIG. 4, like reference numerals are used to identify likelayers and like films having the same functions as the layers and thefilms shown in FIG. 2. As shown in FIG. 4, the magneto-resistance effectfilm 20 is tapered on the side surface at a taper angle of 50 to 80degrees. This taper is generated by the incidence conditions of the ionsfor milling the magneto-resistance effect film 20. The lower shield film10 is a Co type amorphous alloy film or a FeAlSi alloy film. Theelectrode film 8 is made of a Ta alloy, a TaW alloy, alloys of Nb, Mo,W, Cu and Al, or alloys of precious metals such as Ru, Pt, etc. Theelectrode film 8 comprises a multi-layered film (e.g. Ta layer/Ptlayer/Ta layer or Ta layer/Cu layer/Ta layer). The free layer 2 is amulti-layered film in order to prevent diffusion on the interface or torestrict anisotropic dispersion. It has, for example, a multi-layeredstructure of a Co layer/NiFe layer/Co layer.

[0049] Next, a production process of the reproducing head shown in FIG.4 will be explained with reference to FIGS. 11A to 11G.

[0050] To begin with, the lower shield film 10 is formed on a substrate(similar to the substrate 31 shown in FIG. 1) by sputtering or plating,and then the electrode film 8 is formed by vacuum deposition. After thesurface of the electrode film 8 is subjected to ion cleaning, the freelayer 3, the insulating layer 1, the fixing layer 2 and theanti-ferromagnetic film 4 of the magneto-resistance effect film 20 areformed in order. These four layers of the magneto-resistance effect film20 are processed by ion milling. After the resist film 12 having theshape shown in FIG. 11A is formed on the magneto-resistance effect film20 which is so processed, the magnetic domain control films 7 are formed(FIG. 11B), the resist film 12 is dissolved, and the magnetic domaincontrol films 7 on the magneto-resistance effect film 20 are lifted off(FIG. 1C). The insulating film 6 is then formed, and then the resistfilm 13 is formed on this insulating film 6 and is patterned (FIG. 1D).Next, the insulating film 6 is processed by IRE using the resist film 13as a mask. This process step forms the through-hole 21 (FIG. 11E).Incidentally, a stopper film may be formed in advance between theanti-ferromagnetic film 4 and the insulating film 6 in order to preventthe anti-ferromagnetic film 4 from being damaged by RIE. The resist film13 is removed (FIG. 11F) and the upper shield film 9 is formed on theinsulating film 6 (FIG. 11G). In this way, the reproducing TMR headshown in FIG. 4 can be produced.

[0051] Incidentally, the upper shield film 9 shown in FIGS. 3 and 4serves also as the electrode film 5 but in this case, the upper shieldfilm 9 is not smooth and flat in comparison with the construction ofFIG. 1 because the upper shield film 9 has the shape that profiles theinsulating film 6 and the magneto-resistance effect film 20. Therefore,magnetic walls are likely to be defined on the upper shield film 9 inthe proximity of the through-hole 21. To prevent the formation of themagnetic walls, a non-magnetic film may be formed in the proximity ofthe through-hole 21 as a multi-layered shield film 9. It has been foundthat the formation of the magnetic walls can be prevented by forming,for example, a shield film 9 having a multi-layered structure comprisinga NiFe layer/Al₂O₃ layer/NiFe layer, and the shield film 9 contributesto the prevention of fluctuation of the output of the reproducing TMRhead and the occurrence of the noise.

[0052] Next, a reproducing TMR head according to the fourth embodimentwill be explained with reference to FIG. 5.

[0053] In FIG. 5, like reference numerals are used to identify likelayers and films having the same functions as those shown in FIG. 2. Inthe reproducing TMR head shown in FIG. 5, the magneto-resistance effectfilm 20 is tapered, the free layer 3 inside the magneto-resistanceeffect film 20 has a greater width than the other layers 1, 2 and 4, andthe insulating film 6 is so arranged as to be in contact with both endsof the upper surface of the free layer 3. In comparison with theconstruction shown in FIG. 4, the construction of FIG. 5 completelyisolates the magnetic domain control films 7 and the fixing layer 2 bythe insulating film 6, and can prevent with high reliability the leak ofthe current from the fixing layer 2 to the magnetic domain control films7.

[0054] When the reproducing TMR head shown in FIG. 5 is produced, onlythe free layer 3 of the magneto-resistance effect film 20 is firstformed and then milling is effected once so as to process only the freelayer 3. Thereafter, the three layers of the insulating layer 3, thefixing layer 2 and the anti-ferromagnetic film 4 are formed and millingis carried out once again to process these three layers. Alternatively,the four layers of the magneto-resistance effect film 20 are formed allat once, the three layers of the insulating layer 3, the fixing layer 2and the anti-ferromagnetic film 4 are then etched by milling and etchingis stopped on the free layer 3. In either case, the shape shown in FIG.5 can be accomplished. Other production steps and the materials may bethe same as those of the embodiment shown in FIG. 4.

[0055] Next, FIGS. 6 to 9 show the fifth to eighth embodiments wherein ahigh resistivity film 11 is interposed between the magnetic domaincontrol films 7 and the magneto-resistance effect film. This highresistivity film 11 is to prevent the current flowing through themagneto-resistance effect film 20 in the direction of film thicknessfrom leaking to the magnetic domain control films 7, and is made of aninsulating material or a semiconductor.

[0056] The construction of the reproducing TMR shown in FIG. 6 seemsanalogous to the construction shown in FIG. 4, but it is not equippedwith the insulating film 6 but is equipped instead with the highresistivity film 11. The high resistivity film 11 is disposed in such afashion as to cover the side surface of the magneto-resistance effectfilm 20 and the magnetic domain control layers 7 are disposed outsidethe high resistivity film 11. The through-hole is bored in the highresistivity film 11 in the same way as in the case of the insulatingfilm 6 shown in FIG. 4 and the width of this through-hole determines thewidth of the electrode film 5 (serving also as the upper shield film 9)which is in contact with the anti-ferromagnetic film 4, that is, thetrack width.

[0057] The procedure for producing the reproducing TMR head shown inFIG. 6 will be explained briefly. First, the lower shield film 10, theelectrode film 8 and the magneto-resistance effect film 20 are formedserially on the substrate 31 and then the magneto-resistance effect film20 is processed by miling. The high resistivity film 11 is formed on themagneto-resistance effect film 20 by sputtering SiO₂ or Al₂O₃ to a filmthickness of 5 to 10 nm. The adhering condition of the film is adjustedby changing the sputtering condition (particularly, the distance betweenthe substrate and the target) and the high resistivity film 11 havingthe thickness shown in FIG. 6 is formed. Next, the magnetic domaincontrol films 7 are formed. The thickness of the magnetic domain controlfilms 7 is 5 to 20 nm. The magnetic domain control films 7 on themagneto-resistance effect film 20 are removed by lift-off in the sameway as in FIGS. 11B and 11C. The through-hole is formed in the highresistivity film 11 by the same means as the one shown in FIGS. 11D to11F. Thereafter the upper shield film 9 (serving also as the electrodefilm 5) is formed.

[0058] On the other hand, each of the constructions shown in FIGS. 7 to9 is equipped with both the insulating film 6 and the high resistivityfilm 11. The film thickness of the high resistivity film 11 is large atthe upper portion of the side surfaces of the magneto-resistance effectfilm 20 but is uniform at other flat portions. The upper surface of eachmagnetic domain control film is flat and is in conformity with the uppersurface of the magneto-resistance effect film 20. Therefore, theinsulating film 6 has a uniform thickness. Further, the order of eachlayer of the magneto-resistance effect film 20 is exactly opposite tothe order of the constructions shown in FIGS. 2 to 6. In other words,the anti-ferromagnetic film 4, the fixing layer 2, the insulating layer1 and the free layer 3 are disposed in order named from the electrodefilm (8) side. The track width is determined by the spacing of thethrough-hole of the insulating film 6 in entirely the same way as in theconstructions shown in FIGS. 2 to 5.

[0059] In the construction shown in FIG. 8, the lower electrode film 8(serving also as the base film of the magneto-resistance effect film20), too, is processed by milling and the high resistivity film 11 isformed on the side surface portion of the electrode film 8, too. In theconstruction shown in FIG. 9, the high resistivity film 11 extends up toboth end portions of the upper surface of the free layer 3.

[0060] The production process of the reproducing TMR head having theconstruction shown in FIG. 8 will be explained with reference to FIGS.12A to 12G.

[0061] Initially, the lower shield film 10 is formed by sputtering orplating on the substrate (similar to the substrate 31 shown in FIG. 1)and the electrode film 8 is formed by vacuum deposition. After thesurface of the electrode film 8 is cleaned by ion cleaning, theanti-ferromagnetic film 4, the fixing layer 2, the insulating layer 1and the free layer 3 of the magneto-resistance effect film 20 areserially formed. These four layers of the magneto-resistance effect film20 and the electrode film 8 are then processed by ion milling. A resistfilm 42 having the shape of two stages as shown in FIG. 12A is formed onthe magneto-resistance effect film 20 so processed. The high resistivityfilm 11 is formed on this resist film 42 (FIG. 12B). The resist film 42is dissolved and the high resistivity film 11 on the magneto-resistanceeffect film 11 is lifted off. The magnetic domain control films 7 areformed next. The upper surface of the magnetic domain control films 7 ispolished to a flat surface by CMP (Chemical Mechanical Polishing) (FIG.12D). The insulating film 6 and the resist film 43 are serially formedon this control film 7 and the resist film 43 is patterned (FIG. 12E).The insulating film 6 is processed by RIE using this resist film 43 asthe mask. In this way the through-hole 21 can be formed (FIG. 12F).After the resist film 43 is removed, the upper shield film 9 (whichserves also as the electrode film 5) is formed on the insulating film 6(FIG. 12G). As a result, the reproducing TMR head shown in FIG. 8 can befabricated.

[0062] In the reproducing TMR head having each of the constructionsshown in FIGS. 6 to 9, the high resistivity film 11 covers the entireside surface of the magneto-resistance effect film 20 and electricallyisolates the magnetic domain control films 7 from the magneto-resistanceeffect film 20. Therefore, the leakage current flowing from the fixinglayer 2 to the electrode film 8 through the magnetic domain control film7 does not occur, and the current flowing through the magneto-resistanceeffect film 20 in the direction of film thickness can be increased. Inconsequence, detection efficiency of the resistance change ratio of themagneto-resistance effect film 20 due to the spin tunnelmagneto-resistance effect can be improved.

[0063] The constructions shown in FIGS. 6 to 9 reduce the width of theelectrode film 5, which is in contact with the magneto-resistance effectfilm 20, to a smaller width than the width of the insulating film 6 andthe high resistivity film 11 so that the track width becomes smallerthan the width of the magneto-resistance effect film 20, in the same wayas the constructions shown in FIGS. 2 to 4. Therefore, the track widthcan be easily made narrower without reducing the width of themagneto-resistance effect film 20 and the recording density of themagnetic disk of the magnetic recording/reproducing apparatus can beincreased.

[0064] Further, in the constructions shown in FIGS. 7 to 9, the uppersurface of the magnetic domain control films 7 is brought intoconformity with the upper surface of the magneto-resistance effect film20 and is rendered flat. Therefore, the upper shield film 9 (servingalso as the electrode film 5) can keep a uniform thickness with theexception of the portion of the through-hole 21. For this reason, themagnetic wall does not easily develop in the upper shield film 9 andperformance of the upper shield film 9 can be improved.

[0065] Next, the overall construction and operation of a magneticrecording/reproducing apparatus using the reproducing TMR head of eachembodiment of the present invention described above will be explainedwith reference to FIG. 10.

[0066] A recording/reproducing head 210 includes the reproducing TMRhead in any of the constructions shown in FIGS. 2 to 9 and a recordingthin film magnetic head mounted onto the reproducing TMR head. Therecording/reproducing head 210 is supported at the distal end of aspring 211 with its float-up surface facing down. The spring is fittedto a head positioning mechanism 320. The head positioning mechanism 320positions the recording/reproducing head 210 onto a recording medium(hard disk) 110. The recording medium 110 is driven for rotation by aspindle motor 310. When recording is made, the inputted recording datais encoded by an encoder 335 and a recording current is supplied by arecording amplifier 336 to the recording thin film magnetic head. Whenreproduction is made, on the other hand, the current flowing between theelectrode films 5 and 8 of the reproducing TMR head is processed by asignal processing system 330 and the magnetic information of therecording medium 110 is reproduced. More concretely, the current flowingbetween the electrode films 5 and 8 is amplified by a pre-amplifier 331and the data is reproduced by a data reproducing circuit 332 and isdecoded by a decoder 333. A servo detector 334 controls tracking of therecording/reproducing head 210 by using the output signal of thepre-amplifier 331. A controller 340 controls the signal processingoperations described above.

[0067] The magnetic recording/reproducing apparatus shown in FIG. 10 isequipped with the TMR head having any of the constructions of theembodiments of the present invention shown in FIGS. 2 to 9 as thereproducing head of the recording reproducing apparatus. Since this TMRhead can prevent the leak of the current to the magnetic domain controlfilm 7, the signal processing system 330 can detect with high efficiencythe resistance change ratio due to the spin tunnel magneto-resistanceeffect, and a magnetic recording/reproducing apparatus having a highdetection sensitivity at the time of reproduction can be obtained. Sincethe width of the electrode film 5 which is in contact with themagneto-resistance effect film 20 is reduced in this TMR head, the trackwidth is small and the magnetic information of the recording medium 110recorded in a high recording density can be reproduced.

[0068] In this way, the embodiments of the present invention can providethe construction of the recording/reproducing head using the spin tunnelmagneto-resistance effect which head can prevent the leakage current andmoreover has a small track width and high practicality, and the magneticrecording/reproducing apparatus using the recording/reproducing head.

[0069] Next, an embodiment wherein the magnetic sensor according to thepresent invention is applied to a magnetic memory will be explained.

[0070]FIG. 13 is a sectional view showing a magnetic memory according tothis embodiment and FIG. 14 is a plan view showing the magnetic memoryaccording to this embodiment. A first base layer 42, a second base layer43, an anti-ferromagnetic layer 44 and a fixing layer 45 are formed bysputtering, or the like, on a substrate 41. These layers are etched intoa first pattern extending in a first direction. Next, an insulatinglayer 46, a free layer 47 and a third base layer 48 are formed bysputtering, or the like. These layers are etched into a second pattern.The anti-ferromagnetic layer 44, the fixing layer 45, the insulatingfilm 46 and the free layer 47 together constitute a magneto-resistanceeffect film 60 in a region where the first pattern and the secondpattern cross each other. Next, an insulating film 49 is formed andpatterned around the crossing region of the first and second patterns,and an opening 61 is formed at a substantial center of the insulatingfilm 49. An upper electrode 50 is formed on the insulating film 49inclusive of the inside of the opening 61. The upper electrode 50defines a third pattern extending in a second direction crossingorthogonally the first direction and is electrically connected to thefree layer 47 through the third base layer 48 only inside the opening 61of the insulating film 49. Further, a first lower electrode 51 and asecond lower electrode 52 are formed and patterned on a predeterminedregion of the fixing layer 45.

[0071] When a current is caused to flow between the first and secondlower electrodes in the construction described above, the current flowsthrough at least the fixing layer 45, and the direction of magnetizationof the free layer 47 is determined by the flowing direction of thecurrent, so that the data is stored. The magnetic characteristics of theanti-ferromagnetic layer 44 for fixing magnetization of the fixing layer45 are decided so that the direction of magnetization of the free layer47 is parallel or anti-parallel to the direction of magnetization of thefixing layer 45. When the current is caused to flow in the direction offilm thickness of the magneto-resistance effect film 60 by applying avoltage between the upper electrode 50 and the first lower electrode 51or between the upper electrode 50 and the second lower electrode 52, thecurrent flows while tunneling through the insulating film 46, and theelectric resistance of the magneto-resistance effect film 60 changesdepending on whether the directions of magnetization of the free layer47 and the fixing layer 45 are parallel or anti-parallel to each other,due to the spin tunnel magneto-resistance effect (TMR). The data that isstored can be read out by detecting this change. Though this embodimentuses a RAM (Random Access Memory) construction capable of writing thedata, a ROM (Read-only Memory) construction can be employed, too, byomitting the second lower electrode 52. When the ROM construction isemployed, the data may be stored in advance by applying the magneticfield from outside.

[0072] Next, the material of each part will be explained. Silicon orceramics, for example, can be used for the substrate 41. Tantalum (Ta),for example, can be used for the first base layer 42 and the third baselayer 48. A NiFe alloy, for example, can be used for the second baselayer 43. A FeMn alloy or a MnIr alloy, for example, can be used for theanti-ferromagnetic layer 44. A CoFe alloy, for example, can be used forthe fixing layer 45. Al₂O₃, for example, can be used for the insulatingfilms 46 and 49. A CoFe alloy or a NiFe alloy, for example, can be usedfor the free layer 47. Gold (Au), copper (Cu), tantalum (Ta), ruthenium(Ru), etc, for example, can be used for the upper electrode 50, thefirst lower electrode 51 and the second lower electrode 52. In addition,those materials which are described as usable for respective portions inthe description of the foregoing embodiments of the magnetic heads maybe employed, as well.

[0073] As described above, this embodiment provides the magnetic memorywhich can be produced more easily than the conventional processes andwhich can keep stably and satisfactorily film quality and film thicknessof each layer.

What is claimed is:
 1. A spin tunnel magneto-resistance effect typemagnetic sensor comprising: a first insulating film capable of allowinga current to flow while tunneling therethrough; a first magnetic layerformed on a first plane of said first insulating film, and containing aferromagnetic substance; a second magnetic layer formed on a secondplane of said first insulating film, and containing a ferromagneticsubstance; a third magnetic layer formed on said second magnetic layer,and containing an anti-ferromagnetic substance for fixing magnetizationof said second magnetic layer; a second insulting film formed on atleast one of said first and third magnetic layers, and having an openingin a predetermined region; a first electrode electrically connected toone of said first and third magnetic layers only inside said opening ofsaid second insulating film; a second electrode for causing a current toflow between said first electrode and itself through at least said firstand second magnetic layers and said first insulating film; and a pair ofmagnetic domain control films for applying a magnetic bias to said firstmagnetic layer to control the magnetic domain of said first magneticlayer.
 2. A magnetic sensor according to claim 1, wherein: said firstmagnetic layer is so disposed as to hang over said pair of magneticdomain control films.
 3. A magnetic sensor according to claim 2,wherein: said second insulating film includes a high resistivity filmcovering side surfaces of said first magnetic layer, said firstinsulating film, said second magnetic layer and said third magneticlayer; and said pair of magnetic domain control films are formed on saidhigh resistivity film.
 4. A magnetic recording/reproducing apparatuscomprising: medium driving means for driving a magnetic recordingmedium: a head assembly including an electromagnetic induction typemagnetic head as a recording head for recording signals to said magneticrecording medium and said magnetic sensor according to claim 2 as areproducing head for reproducing the signals recorded on said magneticrecording medium; head driving means for driving said head assembly; andsignal processing means for processing recording signals to be appliedto said recording head and reproduction signal output from saidreproducing head.